1. Field of the Invention
The present invention relates in general to a photoreceptor belt control apparatus, for a printer, which steers a photoreceptor belt, and applies tension to and removes tension from the photoreceptor belt. More particularly, the present invention relates to a photoreceptor belt control apparatus for preventing the photoreceptor belt from traveling laterally, and for applying tension to and releasing tension from the photoreceptor belt by driving auxiliary frames that support a steering roller.
2. Description of the Related Art
A general printer, such as a laser printer, forms a latent electrostatic image by scanning a photoreceptor belt using a laser scanning unit, develops the latent electrostatic image with a color ink using a developing unit, and transfers the developed image onto a printing paper.
Referring to FIG. 1, a general printer includes a photoreceptor belt 10 that circulates continuously around a set of rollers 12, 14 and 21 installed in the main body of the printer. The general printer further includes an erase lamp 15 for erasing a surface potential formed on the photoreceptor belt 10, a charger 17 for charging the photoreceptor belt 10 with a predetermined potential, a plurality of laser scanning units (LSU) 18 for scanning the photoreceptor belt 10 with laser beams to form latent electrostatic images for respective colors, and a plurality of developing units 19 for developing the latent electrostatic images.
As the photoreceptor belt 10 circulates around the rollers 12, 14 and 21, it tends to travel laterally, i.e., in the length direction of the rollers 12, 14, and 21. Also, it is necessary to release the tension in the photoreceptor belt 10, for example, upon attachment and detachment of a belt unit including the photoreceptor belt 10 and the rollers 12, 14, and 21.
Referring to FIGS. 1 and 2, a conventional photoreceptor belt control apparatus for the general printer includes a photoreceptor belt steering unit 20 for correcting the lateral travel of the photoreceptor belt 10 on the basis of information detected by a lateral travel detector (not shown), and a tension applying/releasing unit 40 for controlling the tension in the photoreceptor belt 10.
The photoreceptor belt steering unit 20 includes a frame 23 installed on a printer main body 1, a pivot member 25 pivotally installed on the frame 23, a steering roller 21 installed on the pivot member 25 for supporting the photoreceptor belt 10 so that the photoreceptor belt 10 rotates along a fixed path, a pair of stable rollers 27 installed on the frame 23 to prevent the photoreceptor belt 10 from being crumpled as it passes over the steering roller 21, and a control unit 30 installed on the printer main body 1 for controlling the upward and downward (direction indicated by arrow A) tilt of the steering roller 21.
The tension applying/releasing unit 40 includes a guide bar 41 with one end hinged to the center of the pivot member 25, a first cam member 43, an elastic member 45 installed on the outer circumference of the guide bar 41, the elastic member 45 having ends that respectively contact the first cam member 43 and the frame 23, and a control knob 47 for controlling the first cam member 43. The control knob 47 controls the elasticity of the elastic member 45 to adjust the pressure of the steering roller 21 against the photoreceptor belt 10, thereby adjusting the tension in the photoreceptor belt 10.
The pivot member 25 is coupled to the guide bar 41 by a coupling pin 39, and pivots in an X-Y plane about the coupling pin 39. The pivot member 25 pivots in a direction to compensate for an unbalanced pressure that the steering roller 21 applies against the photoreceptor belt 10. A sliding plate 46 is slidably installed on the outer circumference of the guide bar 41 so as to compress the elastic member 45 according to the rotation position of the first cam member 43.
A shaft 21a of the steering roller 21 is inserted into a holding hole 25a formed in the pivot member 25. An elastic piece 26, for pressing the shaft 21a of the steering roller 21 into the holding hole 25a, is installed on the pivot member 25 adjacent to the holding hole 25a.
The control unit 30 includes a driving motor 31 fixed to the printer main body 1, a second cam member 33 whose center is combined with a shaft 31a of the driving motor 31, the second cam member 33 having a cam hole 33a, and a rotating guide protrusion 35 coupled to the pivot member 25 and inserted into the cam hole 33a. The position of the cam hole 33a varies with the rotation of the driving motor 31, thereby changing the relative position of the rotating guide protrusion 35. The steering roller 21 pivots on the guide bar 41 in the direction indicated by arrow A.
When a lateral travel degree of the photoreceptor belt 10 is detected by the lateral travel detector, the second cam member 33 rotates to adjust the tilt of the steering roller 21. The tilt of the steering roller 21 causes the photoreceptor belt 10 to return to its initial lateral position. In this way, the lateral travel of the photoreceptor belt 10 is corrected.
The pair of stable rollers 27 are installed parallel to the steering roller 21, and respectively contact a portion of the photoreceptor belt 10 heading for the steering roller 21 and a portion of the photoreceptor belt 10 that has passed across the steering roller 21. These stable rollers 27 prevent the photoreceptor belt 10 from crumpling.
Although generally thought to be acceptable, the conventional photoreceptor belt control apparatus is not without shortcomings. In particular, the steering roller 21 pivots about the coupling pin 39, which is located at the end of the guide bar 41. This pivoting action requires structure that occupies valuable internal space in a printer main body. The structure includes the pivot member 25, guide bar 41, and frame 23. Thus, the miniaturization of the photoreceptor belt control apparatus is limited.
Also, the first cam member 43 adjusts the elastic force applied to the guide bar 41, and thus the tension in the photoreceptor belt 10 is adjustable. This conventional structure, however, does not allow a convenient retreating movement of the steering roller 21 in the direction indicated by arrow X.